The Stovebolt Site Forums The Shop Area Engine Shop Identifying a 261 in a 1945 Flxible Clipper

Good Afternoon,

We are trying to nail down the build year of a 261 that we have as the power plant in our 1945 Flxible Clipper.

The machined surface near the distributor is not stamped.

There is a casting posterior of the machined surface that reads, "CON4 H31 0".

Any thoughts on where one might find more identifying numbers? What does the CON4 H31 0 tell you folks that can decipher such things?

Here is a photograph of the engine, in situ. Please disregard the temporary rear control wiring. It was in place just to make getting things running and tuned easier as it is 30' to the other end of the rig.

Take Care,

Joshua L. Coder

There should be some numbers cast into the block opposite side from the generator.There are a few websites that show a list of the numbers ,match the numbers to yours and you should have a year and what the engine was used for (truck or car).With no number by the distributor it may be a replacement engine from gm.

The position of the water pump in your photo indicates that the engine is no older than a mid-year 1955. 54 and early 55's have the sane water pump as a 216, located just below the thermostat housing. If you can see the area near the oil pan rail on the generator side of the engine, if there are two large pipe plugs (1/2" NPT), you have a 1959 or later block that can be set up for full flow oil filtering. The casting number opposite the generator location is the best way to get a correct identification.
Jerry

First off, a Flxible, how cool is that!
The CON4, pretty much has no meaning except that the engine came off of conveyor belt 4.

H31 0 is the date code and in this case the block was produced August 31, 1960. H is the eighth letter of the alphabet, 31 is the day followed by a number 0-9, which repeated every 10 years. In this case 261’s were only produced from 54 thru 62.

There is another number, on the same side towards the front of the engine that will further identify your engine. Post that and we can tell you what block you have. The head has similar numbers and a date code as well.

You might also want to check out our 261 article in the Stovebolt Tech Tips

Stovebolt.com 261 Rebuilding Tech Tip

Even though it is written to help those rebuilding an engine, it contains a lot of useful info. Go read it. Now.

Thank you for the help.

After a bit of time with a wire wheel, we were able to find the following number cast into the passenger side of the engine, between the distributor and downdraft tube (breather): 3769925

The number cast into the manifold is as follows: 3836850, with the GM 3 below.

We'll have a look, around lunch, for the pipe plugs. Currently there is no filter setup on the engine. There is a mechanical oil pressure sensor installed in that general location.

We'll have a look at the 261 article, as well.

Thanks again for the interest and the help.

Edited to add the "3" to the casting number.

Take Care,

Joshua L. Coder

As a related aside, Flxible documents show that this bus left the factory with the following engine: BGD 688104

Does that number look correct and/or what does it say about the original motor?

Take Care,

Joshua L. Coder

ID info from Tim Lederman's website and picture of the serial number location.

Also, check out http://flxibleowners.org/serial-numbers-6700-6800/

Thank you.

The serial number area is unstamped.

I am a member over at FOI and have used their serial number tool to identify the original engine number shown/noted above. Does that number tell anyone anything?

Take Care,

Joshua L. Coder

The block was made from 59 thru 61 which coincides with the date code. So we can safely say the block is a 261 forged in 1960. Look for the head code. It’s located on the head between the valve cover and the manifold on the drivers side. The date code for the head is under the valve cover on the passenger side.

It could have been a NOS engine that never was installed by a vehicle manufacturer.

I could not find the page for a 1960 but here is one for a 1959 Chevy truck.
The serial number can be used to identify what type/size truck it was installed in and what options (RPO) was used.
At one time and in some states, the engine number may be used in the title.
In your case, the engine is a transplant so I would think it's not a real concern.

The engine is obviously much newer than the bus, since 261's didn't begin production until 1954, and the 1959 casting code on your engine confirms that. The engine that was originally installed would probably have been a 235 with spray oiling of the connecting rods and Babbit bearing rods. The 261 is a definite upgrade, power and reliability-wise. 235's that were built from 1941 to 53 were basically upsized 216's and were only used in medium-duty and larger trucks. Passenger cars didn't get a 235 until 1950, and then only ones with Powerglide automatic transmissions.
Jerry

I believe this is the head code: 3836850 (I errantly stated, above, that it was cast into the manifold. That was/is incorrect. It is cast into the head, between the valve cover and the manifold.)

Removing the valve cover revealed the following, both cast into the head, on the driver side: "CON9" & a bit posterior to that "K 21 8"

I checked again, with better light, and still find nothing in the way of a serial number on the block. I can keep cleaning/wheeling and see if there is something on the far end, but it seems unlikely. Aside from my cleaning/wheeling/scraping it looks wholly unmolested. (See attached photograph.)

Take Care,

Joshua L. Coder

That blank pad at the distributor usually indicates that the block is a replacement item, one that a dealer would stamp to match the failed engine they were removing. Since some stares used the engine number as a vehicle ID number, that was necessary to keep the paper trail correct on the vehicle. Does the engine have the "captain's bars" casting, two vertical bars cast into the block just above the starter area? Those marks, along with a similar pair of bars cast into the block on the opposite side of the engine, and the big oil ports in the latest-model 261 are all ways to distinguish the 261 from the similar-looking 235's. The absolutely positive way to identify a 261 is to pull the cylinder head and measure the bore size. 235's have a 3 9/16" bore- - - -261's are 3 3/4". Both engines run the same crankshaft- - - -a 3 15/16" stroke.
Jerry

Jerry,

The engine does indeed have the Captain's Bars on the passenger side.

The oil ports are present, on the driver side. The port nearest the 'pin' has a pipe plug in it. The further back has the mechanical oil sensor installed in it.

It's difficult to photograph due to the exhaust setup, but attached is a photograph attempting to show both ports.

In removing the valve cover I had a bit of a sinking feeling as I saw a mess of little brass/bronze looking pieces. I scratched my head for quite a while trying to identify them and/or figure out from where they could be coming. I picked all of them out that I could see and rolled the engine over by hand many times to see if anything appeared out of the ordinary. Not seeing anything, and I am hardly qualified to know if I am seeing anything, I decided to button it up and solve that mystery on another day. As I went to put the valve cover back on I noticed the same exact pieces stuffed in the valve cover cap. It appears it is/was the filter media of choice for the valve cover cap. To this end, would there be sufficient negative pressure in the valve cover to suck those in or are they just falling out of the cap? It seems like a guy should find a new/different cap, but perhaps there is no harm in them being in the valve train?

Take Care,

Joshua L. Coder

If the serial number pad was unstamped, the casting date may be misleading. They made a "crate engine" 261 using the 54 water pump style but with a later casting date. These engines were built to be an easy replacement for tired 216's in large trucks using the old engines accessories. A more "bolt in" operation.

Greg, the first photo the OP posted shows a low water pump engine, and the late casting/high water pump engines didn't have the full flow oil filter plumbing. I believe he's got a late model "crate" engine in an early bus chassis, probably a replacement for a spray-oiler 235.
Jerry

Murphy's Law says the particles from the breather cap is also in the oil pan just waiting to wreck you main bearings if it hasn't already.
I would do a major flush and check the bearings before attempting to start the engine.

In your transmission posting, there is a picture of a Clark 204VO connected to a GMC engine. There is a good chance that your transmission is original to the bus. If you want to go back original, I would do a research on GMC engines. The 261 is Chevrolet. In the early days (pre 50's) GM worked closely with Flxible so my guess is they would also use the same engines of the current military equipment.

Super news on Murphy's Law. Best to figure it out now then somewhere down the road/on the road, I suppose. We will have to have a look around the www and see how one goes about flushing the oil system.

We changed fluids this past Saturday and did not find any metal in the drain(ed) oil. That said, we did not pull the pan. We need to do that anyway as some ham-fisted previous owner must have stripped the drain plug and fixed it with and oversized strip-o-matic 200 drain plug which is also stripped. What is the recommended repair on a stripped out drain plug hole? The rest of the pan, while showing its' age, appears serviceable.

All of this discussion is the result of finding coolant leaking from between the rear of the engine and the bellhousing after changing fluids. Removing the transmission, pressure plate, clutch, flywheel and bellhousing revealed one failing core plug and another that looked OK, but was leaking. The core plug that is higher and centered appears to be in 'backwards' compared to all others. By this I mean you do not see any cup, just a flat surface. (You will need to zoom in on the attached photograph to see what I am trying to describe.)

Is there anything special about the core plugs for this engine?

Take Care,

Joshua L. Coder

That big core plug centered on the block is a flat design which does not have a shoulder. It is slightly convex-shaped, and the outer edge fits into a shallow counterbore in the block. Once the plug is positioned in the block, a firm tap with a big hammer expands the outside diameter and seals it. Putting a little brush-on non hardening gasket sealer on the edge of the plug helps seal the coolant. The smaller plug that's visible lower down on the back of the block is there to plug the camshaft bore, and seals oil , not coolant.
Jerry

Thank you for the clarification on which plug is which and what type of plug is needed.

Both the large center plug and the lower plug show signs of leakage. As such, we will replace both since we have access.

The tiny plugs, of which there are two, do not show signs of leakage and seem well seated. As such, we will leave these alone.

Thanks again for the help.

Take Care,

Joshua L. Coder

The head code is for a 261 produced between 54 thru 62. The date code, K21 8, translates into November 21, 1958.

From what I been reading, Flxible Clippers never came with Chevy engines. They used a Buick straight eight and a GM diesel option, so the number BGD 688104 is more than likely not Chevy. You may have better luck finding out what engine came with your bus on a Flxible site.

If only Bill LePage was still with us. I'm sure he would have been a big help to you. Here are some pictures of his bis:
https://www.flickr.com/photos/29923040@N07/albums/72157639879861156

Military GMC engine?

That is extraordinary work on that bus. I had not seen that, and I thought I had seen all of the 40's Flx's the web had to offer. I've also not seen a roof raise on a Flxible.

Our parts bus is a 1947 Clipper. It's bigger than Dutch (our user bus), but very similar otherwise. It has been recovered with a Y-Block and Transimatic (sp), both of which appear stuck. We did not buy it for the engine or drive train, rather all of the other parts made of unobtainium.


Take Care,

Joshua L. Coder

After a bit more work on the 261 we have had it on the road a number of times. Just short shakedown runs, for the most part. Most recently, we took it to school for the first day of school for our 3rd grader and 6th grader. It was a hit, for them, and most everyone else we encountered.

It is about 15 minutes into town, then about 15 minutes of monkeying around, then about 15 minutes back home. About 5 minutes into the trip back home the engine seemed to be missing. As best I can describe it, it seemed to lack power and I had to stay in the foot feed to keep it running. We had plenty of fuel, so I believe it was not fuel related. I am leaning towards ignition, but would like to hear from those of you that know about such things. We are running what appears to be a 'stock' coil/distributor setup. The coil being mounted to the engine on what would be the passenger side. As received from the PO, there was not a ballast resistor in the coil circuit. Is it possible that running full voltage to the coil all the time could cause issues after a certain amount of run time, or should we be looking elsewhere?

When it happened, it seemed like it was also almost backfiring (though I suspect that is not the right way to describe it), especially when letting off the foot feed.

It pretty much died as we pulled into the parking spot at home. It would not restart immediately, but did a bit later once it 'cooled off'.

It never ran over 180F on the gauge, so we are rather certain it was not/is not an overheating issue.

Any/all thoughts/questions are appreciated.

Take Care,

Joshua L. Coder

If 6 volts, not need a ballast resistor.

Ed

Thanks Ed.

It is a 12V system.

Thanks,

Joshua L. Coder

No resister with 12 volts will damage the points fairly rapidly. Pull the distributor cap pry the points apart. I'll bet that they are not shiny.

The coil is a Delco Remy 1115043, marked 12V.

In measuring the resistance, I find 4.7-4.8 ohms across the primary and 5.75 k-ohms across the secondary.

I have searched the interwebs to the best of my abilities (which admittedly are not great - my abilities that is) and not found anything definitive on what these readings should be. That said, they seem OK to me and would suggest a ballast resistor is NOT needed.

I pulled the cap and rotor and had a look at the points. As near as I can tell, they look like I would expect points to look.

I let the engine idle for 15 minutes and the coil is not remotely hot. It is about the same temperature as the valve cover. This was using my hand to measure temperature, not an actual temperature sensing instrument.

I'm not saying the ignition is not the issue, but if the above holds true, what else should we be looking for/at to help with the issue? Could it be fuel related?

I ran her around the section and up and down the county road last night and it sure seems like duration of run is what makes the issue show up. There is a marked loss of power, which is unwelcome as even at full power the old bus cannot get out of its' own way, and a distinctive backfire like sound when I let off the foot feed.

Take Care,

Joshua L. Coder

The coil will only deliver enough voltage to fire the plugs. This rises dramatically when the engine is loaded (as opposed to idling).

The odd thing is it will run just fine, not just idle but running down the road at as close to road speed as I care to drive it, without issue. After some amount of time, which no doubt equates to heat build-up, it starts to behave as described earlier.

I've not had it happen, ever, idling and I have let it idle for long periods of time just to observe. By long periods I mean hour(s).

I have not tested the coil when it is behaving as described. Last night I let it come up to temp, then pulled the coil and measured the aforementioned resistances. Perhaps I should run it until it starts acting up and re-check the resistances?

Thanks,

Joshua L. Coder

While you say that your points "look like I would expect points to look", they will not remain that way for very long without a ballast resistor.
Its hard to tell you from here, what is causing your poor running issues, but is easy for me to steer you in the right direction to keep you from having another reason for your engine to have a poor running issue in the near future.

As you have alluded to, it is best to do your diagnoses at the exact time the poor running issue takes place.
When it acts up again, be prepared to immediately do a spark test at a spark plug, and/or goose the throttle while looking down the throat of the carburetor to see if there is a squirt of gas entering from the accelerator pump (this will let you know that there is fuel in the bowl of the carburetor).

At the risk of being argumentative, I believe this ignition does not need the resistor. From what I have been able to find online, this coil is to be run without a resistor. If it were to be run with a resistor, it would 1) Say as much if it were a couple decades younger, or 2) Have a much lower resistance on the primary. (Something in the less than an ohm to just over an ohm.)

That said, I should check the distributor and see what the specs are on it, as perhaps it is not meant to be run on a 12-volt coil.

I appreciate the help and suggestions, so please do not interpret my comments/replies as dismissive of your suggestions.

Goosing it while the issue is present should be easy enough with some help. Likewise, checking spark while acting up seems an easy enough ask as well. We will try one or both of those.

Thanks,

Joshua L. Coder

I know you are not trying to be argumentative, and I certainly appreciate that! But I am not sure what online resource you have been using for that coil. That Delco number was used for quite a few applications, including 1950s through 1960s chevrolets and, interestingly enough, Studebakers, among others. Chevrolet even used that coil for the bigger W motors and was over the counter for quite a few years. All of those applications used a ballest resistor. You have to use a resistor with a coil that designed to be used with a resistor. The wiring for these coils generally provides a full 12 volts when the key is on start (bypass the resistor) and then when you release the key or starter button from start, the bypass ends and the voltage flows through the resistor which knocks down the voltage to the coil to like 8 volts or so which not only protects the points from over heating, pitting and burning (which were designed originally for 6 volt applications), but also to keep the coil from over heating.

Now it is true that some later coils were designed to be used without an external resistor. The Delco coil you listed does not appear to be one of them. Besides killing the points, over heating the coil is not good for the coil.

The points do not function at their best if the point contact surface is pitted, rough or badly worn. And frankly, you cant really tell whether the points are rough or pitted by eyeballing them, unless of course the pitting is really bad. Years ago, mechanics would file the points down with a thin point file to get more service life out of a set of points. Turns out, while this workd for a bit, it was not optimal. Points are not that expensive, neither is a firewall ballest resistor.

If I understand correcty, this truck was converted from a 6 volt to 12 volts at some point. Six volt systems did not need or use a ballest resistor. That came about with the change to 12 volts and a resistor was the easisest way to deal with the increased voltage early on. You might consider taking a close look at your wiring (ignition switch, starter solonoid/button), and ignition (coil and distributor). You should then sort out a way to add in the resistor (12 volts when turning over and starting via a bypass, knocked down voltage once the motor is running.)

I am not saying this is your problem, but it could very well be part of the problem.

Usually the coil is marked “Internal Resistor “ in most cases. There’s always the exception.

Good Evening,

I decided to take the shot-gun approach and replace everything that 'could' be an issue. My thinking being if it fixed the issue, great, and I can always go backwards to see where the issue was; or not. If it did not fix the issue, at least we would know that new parts everywhere in the ignition 'should' eliminate the ignition as the issue.

As my coil is long obsolete, my parts guy crossed it and had the crossed coil in stock. It is a 12V coil. NO EXTERNAL RESISTOR NEEDED is printed on the coil. Furthermore, the instructions say in bold print NOT TO USE WITH A RESISTOR OR RESISTOR WIRE. So, new coil - check.

I removed the old points and while they were not perfect, they were not the worst I have seen. There was, however, evidence of arcing. I am not sure I would say pitted, but certainly not great. So, new points - check.

I did not bother testing the old condenser, since I was going for parts and they are - in the big picture, rather inexpensive. I will check the old condenser and see what it shows on a meter. So, new condenser - check.

In reading online I found the points should be set to .016 for this motor. Points are set to .016 with feeler gauge. While setting the points I noticed the rotor can spin - if I try to spin it - almost enough to come off a lobe. Not quite, but almost. Is that too much 'free' rotational movement? It is moving the entire shaft, it's not the rotor moving on the shaft.

The motor seems to have more power and after the longest drive around the countryside, including some decent hill climbs, I would say the issue is less prevalent, yet not completely gone. After 15, or so, minutes of driving I believe I have less power. Additionally, when I am really into the foot feed and let off, I get a backfire. This happens whether driving and letting off the foot feed or revving the engine and letting off. The backfire is out of the exhaust, not the carburetor, as I tested after dark to be sure. I am not sure if it matters, but it is a backfire on one of the last three (3) cylinders, as it comes out of the the 'back' manifold.

There is a noticeable hesitation coming off idle if you goose it. If you roll into the foot feed, it is smooth all the way from idle to red line. (I have no idea what red line is, as I do not have a functioning tach, but suffice to say it is as wide open as it will go.) If you goose it, you can just about stall it, if you do not let off the foot feed. This is not a new issue, just an issue I did not previously mention.

I did NOT gap the plugs before the test drive. I did pull them, once things cooled off a bit, and set all of them to .039, which is what I found online. (Between .036 and .040 is what I read.) All of the plugs looked exactly the same. I would describe them as tan in color on the electrode (both center and side - if that makes sense) and black on the ring around the bottom, below the threads. I can post a photograph if my description is not painting the picture. It is worth note that all of the plugs were gapped to @.019 when I pulled them.

I am all ears on where we go next and expect, I think, it will be the carburetor. Since we may be going here, and I am not sure why this just now dawned on me, it is worth mentioning that I am running a Rochester B - single barrel carb, with the hot-air choke. A massive air cleaner, which looks like an old oil-bath, but is not. I have not the first idea if it is correct, but it came on the engine so I have been using it. Again, if photographs of any/all of this is helpful, please let me know and I will take and post them.

Thanks,

Joshua L. Coder

"While setting the points I noticed the rotor can spin - if I try to spin it - almost enough to come off a lobe. Not quite, but almost. Is that too much 'free' rotational movement? It is moving the entire shaft, it's not the rotor moving on the shaft."

Is there any felt resistance when you "spin" the rotor? Does the shaft remain stationary when you spin the rotor?
If this were my engine, I would double check the point gap to see if it is still set at .016.
If it has moved off of that setting, it will act like moving the timing off of specs, causing a backfire.
If that all checks out, check your timing with a timing light.

Not much, if any, felt resistance. It does not free spin, but there is not much more than friction making it not free spinning. The shaft spins with the rotor. I can get the exact same spin by grabbing the lobed portion and spinning it. I could video the movement, but I do not have a YT channel or another option for getting it to the masses.

I will double check the gap.

10-4 on the timing. I'm sure it is not perfectly in time, but close. That said, I will still check it.

Thanks,

Joshua L. Coder